One of the greatest problems facing the distributors of vaccines in underdeveloped countries is that their viability can be destroyed by storage at improper temperatures. In general, a vaccine must be stored between +2° C. and +8° C. This is an especially difficult problem because, in many regions, this temperature must be maintained in the absence of a reliable (and potentially of any) supply of electricity to run a refrigerator, and this results in an unacceptably high proportion of all vaccines being ineffective by the time they reach their intended target.
Similar problems arise with the storage of food, particularly perishable food items, and packaged beverages such as canned or bottled drinks required to support aid workers and the local population in such circumstances.
It is natural that refrigerators that rely upon alternative sources of energy have been sought, and photovoltaic generation of electricity from sunlight has been seen as the most promising. A problem with any device that relies upon the sun as a source of energy is that the source is unavailable during night time. Conventionally, solar-powered refrigeration apparatus is provided with a rechargeable battery that is charged during daylight and which runs the apparatus at night. However, it is well known that the life of rechargeable batteries is diminished by exposure to high temperature. Failure of the battery can occur with little warning, meaning that the refrigerator can stop working resulting in spoiled contents. The life of the battery is typically much less than other components of a refrigerator: typically no more than five years for the battery, whereas the refrigerator as a whole may last twenty.
In view of these problems, the World Health Organisation (WHO)—the organisation that sets the standards for vaccine refrigerators—now encourages the use of batteryless solar refrigerators in distribution chain for vaccines in future.
One approach to meeting this requirement is to include a cold reservoir within the refrigerator, separated from a payload space of the refrigerator by a thermal barrier. The cold reservoir is a thermal mass that is cooled to a low temperature (perhaps as low as −30° C.) while solar power is available. When power becomes unavailable, the reservoir can absorb heat from the payload space. An important disadvantage of this arrangement is that it is difficult to maintain the temperature of the payload within the required temperature range. This type of apparatus presents a particular risk of overcooling vaccines: freezing can result in their immediate destruction. Freezing can also destroy many food items, such as fresh vegetables, or cause containers that contain water or other water-based beverages to burst.
It is against this background that the present invention has been conceived. The applicants have recognised that there is a need for an apparatus and/or method for reliably cooling items, such as packaged beverages, within a desired temperature range for extended periods without requiring a constant source of mains electrical power.
The present applicants have previously proposed a new form of refrigeration apparatus which addresses the above problems. This apparatus, which is the subject of co-pending patent application no. PCT/GB2010/051129, permits a refrigerated storage space to be maintained within a temperature range of 4-8° C. for up to 30 days following a loss of electrical power.
The applicants have recognised that the technical principles employed in this apparatus may be adapted for use in an apparatus or method for cooling packaged beverages, such as canned or bottled drinks. The demand for chilled beverages is high even in underdeveloped countries since these generally coincide with regions having a hot climate with high average annual temperatures.
Embodiments of the invention may therefore provide an apparatus or a method for cooling a plurality of packaged beverages and maintaining same within a desired temperature range for extended periods of time without a continuous external supply of electrical power. Other aims and advantages of the invention will become apparent from the following description, claims and drawings.